Volume 56, Issue 2, Pages 287-297 (August 2009) A New Generation of Optical Diagnostics for Bladder Cancer: Technology, Diagnostic Accuracy, and Future Applications  Evelyne C.C. Cauberg, Daniël M. de Bruin, Dirk J. Faber, Ton G. van Leeuwen, Jean J.M.C.H. de la Rosette, Theo M. de Reijke  European Urology  Volume 56, Issue 2, Pages 287-297 (August 2009) DOI: 10.1016/j.eururo.2009.02.033 Copyright © 2009 European Association of Urology Terms and Conditions

Fig. 1 Light that does not excite a molecule into one of the energy levels of the excited states (as with fluorescence) may still force it into a so-called virtual state. This virtual state will be extremely short lived and the energy of the incident photon will be quickly reradiated, most likely as a photon with the same wavelength (elastic scattering). When nuclear motion (eg, vibration) occurs during the lifetime of the virtual state, the molecule can relax to a higher vibrational level of the ground state while emitting a photon of longer wavelength. This process is called Raman scattering. Each molecule has unique vibrational energy levels, with their corresponding wavelength shifts. All of the shifted wavelengths from the different molecules in tissue, when combined, form the Raman spectrum, which is a function of the molecular composition of the tissue investigated. Note that the specific process described in this paper is called Stokes-Raman scattering; more variations of Raman scattering are possible but are less likely to occur. European Urology 2009 56, 287-297DOI: (10.1016/j.eururo.2009.02.033) Copyright © 2009 European Association of Urology Terms and Conditions

Fig. 2 Raman spectroscopy: Raman spectra of normal urothelium in blue and bladder tumour in red. (Courtesy of M. Grimbergen, University Medical Center Utrecht, Utrecht, the Netherlands). European Urology 2009 56, 287-297DOI: (10.1016/j.eururo.2009.02.033) Copyright © 2009 European Association of Urology Terms and Conditions

Fig. 3 Optical coherence tomography (OCT) measures light reflectivity versus depth. It is based on white-light interferometry, in which interference signals are only detected if the light in the sample and in the reference arm has travelled equal distances. Thus, by varying the length of the reference arm, the imaging location in the tissue can be controlled. Modern embodiments of OCT do not use moving reference mirrors; instead, technical complexity is shifted towards either the light source (which sequentially provides each wavelength within the source bandwidth at high speed) or the detector (which detects each wavelength within the source bandwidth in parallel). European Urology 2009 56, 287-297DOI: (10.1016/j.eururo.2009.02.033) Copyright © 2009 European Association of Urology Terms and Conditions

Fig. 4 Optical coherence tomography (OCT) image of papillary bladder urothelial cell carcinoma (UCC) on the left and the corresponding haematoxylin and eosin–stained histology on the right (TaG2 UCC). European Urology 2009 56, 287-297DOI: (10.1016/j.eururo.2009.02.033) Copyright © 2009 European Association of Urology Terms and Conditions

Fig. 5 Photodynamic diagnosis (PDD) is based on different concentrations of fluorescence molecules in normal and pathologic tissue. When a fluorescent molecule absorbs light of the appropriate wavelength, it is excited from the ground state (S0) to a higher energy level of the first excited state (S1) before relaxing to the lowest vibrational energy level of S1. Subsequently, the dye returns to the ground state while emitting a photon of lower energy (higher wavelength) than that used for excitation. Appropriate filtering separates the emitted light from the excitation. European Urology 2009 56, 287-297DOI: (10.1016/j.eururo.2009.02.033) Copyright © 2009 European Association of Urology Terms and Conditions

Fig. 6 Photodynamic diagnosis (PDD): Detection of carcinoma in situ with white light on the left and PDD on the right. European Urology 2009 56, 287-297DOI: (10.1016/j.eururo.2009.02.033) Copyright © 2009 European Association of Urology Terms and Conditions

Fig. 7 Narrow-band imaging (NBI) is based on the phenomenon that the depth of light penetration increases with wavelength. Tissue is illuminated with light centred around 415nm (blue) and 540nm (green), which are both absorbed by haemoglobin more strongly than by other tissue. The blue light enhances the superficial capillary network, whereas the green light enhances the visibility of deeper vessels. European Urology 2009 56, 287-297DOI: (10.1016/j.eururo.2009.02.033) Copyright © 2009 European Association of Urology Terms and Conditions

Fig. 8 Narrow-band imaging (NBI): Detection of a papillary bladder tumour with white light on the left and NBI on the right. European Urology 2009 56, 287-297DOI: (10.1016/j.eururo.2009.02.033) Copyright © 2009 European Association of Urology Terms and Conditions